Antifungal susceptibility of Sporothrix schenckii complex biofilms

Abstract

Sporotrichosis, caused by species of Sporothrix schenckii complex, is the most prevalent subcutaneous mycosis in many areas of Latin America. The aim of this study was to evaluate the ability of Sporothrix spp. to form biofilms in vitro and to characterize the growth kinetics, morphology, and antifungal susceptibility of biofilms against classical antifungals. We investigated the ability of strains to produce biofilms in vitro and determined the effects of exposure to amphotericin B, itraconazole, caspofungin, ketoconazole, voriconazole, and fluconazole at minimum inhibitory concentration (MIC) against planktonic form and at 10× MIC and 50× MIC on the biomass and metabolic activity of these biofilms. Biofilm structure was analyzed by optical microscopy using Congo-red staining, confocal and scanning electron microscopy. Strains were classified for biofilm-forming ability, through the analysis of absorbance of crystal violet retained by biomass of mature biofilms. We found that all S. brasiliensis (n = 10), S. schenckii sensu stricto (n = 2), S. globosa (n = 2), and S. mexicana (n = 4) strains were strong biofilm-producers. The analyzed biofilms had dense network of hyphae and conidia immersed in extracellular matrix, with presence of water channels. Antifungal drugs at the three tested concentrations showed different effects on biomass and metabolic activity of biofilms. However, the best inhibitory response was observed with 50× MIC of amphotericin B and caspofungin, which reduced these parameters. Furthermore, high drug concentrations, especially amphotericin B and caspofungin, showed antifungal activity against these biofilms, probably because they damaged the architecture and extracellular matrix, allowing diffusion of the drugs.

Heat Shock Protein 60, Insights to Its Importance in Histoplasma capsulatum: From Biofilm Formation to Host-Interaction

“…After 144 h, both strains produced consistent and mature biofilms, reaching the stationary phase between 144 and 168 h. Compared to other fungal pathogens, as Candida spp. (Sańchez-Vargas et al, 2013;Chandra and Mukherjee, 2015) and Cryptococcus neoformans (Martinez and Casadevall, 2007), our results showed that H. capsulatum exhibits a slower growth as a biofilm structure, similar to those found on Paracoccidioides brasiliensis (Sardi et al, 2015) and Sporothrix schenckii complex (Brilhante et al, 2018) biofilms. Also, EH-315 formed a more robust biofilm compared to G186A, corroborating with the findings of Goncalves et al (2020).…”

Chronic Meningitis and Hydrocephalus due to Sporothrix brasiliensis in Immunocompetent Adults: A Challenging Entity

“…In addition, it has been suggested that, at least in experimental models, S. brasiliensis is more virulent in vivo than the other species [ 9 ]. In vitro, it has also been shown that Sporothrix brasiliensis has a greater ability to disarm murine macrophages, promoting its survival within macrophages (L. Rossato, PhD, S. A. Almeida, PhD, 2017, unpublished data), and to form biofilms [ 10 ]. In fact, biofilm-like structures were observed in patient 2’s CSF ( Figure 1C ), which may help to explain the recurrent hydrocephalus shunt catheter obstructions.…”

In vitro inhibitory effect of statins on planktonic cells and biofilms of the Sporothrix schenckii species complex

“…Biofilm formation of Sporothrix species filamentous forms was performed according to Brilhante et al [3]. An aliquot of 200 µl containing 1×10 6 conidia ml -1 was prepared in RPMI 1640 medium and added to 96-well microplates.…”

“…In order to establish themselves in the host organism, fungi have several virulence factors, including the ability to form biofilms, which are composed of cells that form microcolonies attached to a substrate recognized by the extracellular matrix, which allows or detects whether the microorganism is in a hostile or protected environment regarding host immune defence [3][4][5]. Among the virulence factors that contribute to the survival of S. schenckii complex species, biofilm formation has been described for both filamentous and yeast forms [3][4][5][6].…”